Temperature measuring apparatus and temperature measuring method

ABSTRACT

A temperature measuring apparatus includes a light source, a first splitter, a second splitter, a reference beam reflector, an optical path length adjuster, a reference beam transmitting member, a first to an nth measuring beam transmitting member and a photodetector. The temperature measuring apparatus further includes an attenuator that attenuates the reference beam reflected from the reference beam reflector to thereby make an intensity thereof closer to an intensity of the measurement beam reflected from the temperature measurement object.

CROSS REFERENCE

This application is a division of and is based upon and claims thebenefit of priority under 35 U.S.C. §120 to U.S. Ser. No. 13/476,264,filed May 21, 2012, which claims the benefit of priority to 12/043,654,filed Mar. 6, 2008, now U.S. Pat. No. 8,182,142, issued May 22, 2012,which claims the benefit of U.S. Provisional Application No. 60/938,714,filed on May 18, 2007, and also claims the benefit of priority under 35U.S.C. §119 from Japanese Patent Application No. 2007-057145, filed Mar.7, 2007. The present application also claims the benefit of priority toeach of the foregoing applications and entire contents of which areincorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a temperature measuring apparatus and atemperature measuring method capable of accurately measuring atemperature of, e.g., an a front surface, a rear surface and an innerlayer of an object such as a semiconductor wafer, a liquid crystaldisplay substrate and the like.

BACKGROUND OF THE INVENTION

In general, accurate measurement of a temperature of a substrate (e.g.,a semiconductor wafer) to be processed by a substrate processingapparatus is very important in controlling the shape and property of afilm, a hole and the like formed thereon by various processes such asfilm forming, etching and the like. For this reason, various methods ofmeasuring a temperature of a semiconductor wafer, including ameasurement method using a resistance thermometer or a fluorescentthermometer for measuring a temperature of a rear surface of a substrateand the like, have been performed.

In recent years, a temperature measurement technology using a lowcoherence interferometer capable of directly measuring a temperature ofa wafer, which was difficult by the above method, has been proposed.

Further, in the temperature measurement technology using the lowcoherence interferometer as described above, there is proposed a method(see, for example, Patent Document 1) including the steps of: dividing alight beam originated from a light source into a measurement beam fortemperature measurement and a reference beam by using a first splitter;dividing the measurement beam into n number of measurement beams byusing a second splitter to irradiate the n number of measurement beamsonto n number of measurement points; measuring an interference ofreflected beams of the n number of measurement beams and a reflectedbeam of the reference beam reflected by a reference beam reflector; andmeasuring temperatures of a plurality of measurement points at the sametime. Using such a technology, it is possible to simultaneously measuretemperatures of a plurality of measurement points with simpleconfiguration.

-   (Patent Document 1) Japanese Patent Application Publication No.    2006-112826

SUMMARY OF THE INVENTION

In the above-described prior art, it is possible to simultaneouslymeasure temperatures of a plurality of measurement points with a simpleconfiguration. However, in the prior art discussed above, the light beamgenerated from the light source is splitted into the measurement beamfor the temperature measurement and the reference beam by the firstsplitter, and then the measurement beam is splitted again into n numberof measuring beams by the second splitter. Therefore, if the number ofmeasurement points is increased, the level difference between thereflected beams of thus splitted measuring beams and the reflectedreference beam reflected by the reference beam reflector becomesgreater. This causes a deterioration in the S/N ratio of theinterference signals therebetween, and makes it difficult to perform ahigh-accuracy measurement.

In view of the above, the present invention provides a temperaturemeasurement apparatus and method capable of simultaneously measuringtemperatures of a plurality of measurement points with a higher accuracythan in the prior art, and efficiently performing a substrate process orthe like with a higher accuracy.

In accordance with a first aspect of the present invention, there isprovided a temperature measuring apparatus including a light source; afirst splitter for dividing a light beam emanated from the light sourceinto a measurement beam and a reference beam; at least one secondsplitter for dividing the measurement beam coming from the firstsplitter into a first to an nth measuring beam; a reference beamreflector for reflecting the reference beam coming from the firstsplitter; an optical path length adjuster for adjusting an optical pathlength of the reference beam reflected from the reference beamreflector; a reference beam transmitting member for transmitting thereference beam coming from the first splitter to a reference beamirradiation position from which the reference beam is irradiated ontothe reference beam reflector; a first to an nth measuring beamtransmitting member for transmitting the first to the nth measuring beamcoming from the second splitters to measuring beam irradiating positionsfrom which the measurement beams are irradiated onto a first to an nthmeasurement points of a temperature measurement object; a photodetectorfor measuring an interference between the reference beam reflected fromthe reference beam reflector and the first to the nth measuring beamreflected from the temperature measurement object, wherein the opticalpath lengths of the first to the nth measuring beam from the secondsplitter to the temperature measurement object are different from eachother; and an attenuator that attenuates the reference beam reflectedfrom the reference beam reflector such that an intensity thereof becomescloser to an intensity of the measurement beam reflected from thetemperature measurement object.

It is preferable that the attenuator attenuates a light beam passingtherethrough to 1/√{square root over (n)} of an original intensitythereof.

In accordance with a second aspect of the present invention, there isprovided a temperature measuring apparatus including a light source; asplitter for dividing a light beam emanated from the light source into areference beam and a first to an nth measuring beam; a reference beamreflector for reflecting the reference beam coming from the splitter; anoptical path length adjuster for adjusting an optical path length of thereference beam reflected from the reference beam reflector; a referencebeam transmitting member for transmitting the reference beam coming fromthe splitter to a reference beam irradiation position from which thereference beam is irradiated onto the reference beam reflector; a firstto an nth measuring beam transmitting member for transmitting the firstto the nth measuring beam coming from the splitter to measuring beamirradiating positions from which the measurement beams are irradiatedonto a first to an nth measurement points of a temperature measurementobject; and a photodetector for measuring an interference between thereference beam reflected from the reference beam reflector and the firstto the nth measuring beam reflected from the temperature measurementobject, wherein the optical path lengths of the first to the nthmeasuring beam from the splitter to the temperature measurement objectare different from each other.

In accordance with a third aspect of the present invention, there isprovided a temperature measuring apparatus including a light source; afirst splitter for dividing a light beam emanated from the light sourceinto a measurement beam and a reference beam; at least one secondsplitter for dividing the measurement beam coming from the firstsplitter into a first to an nth measuring beam; a reference beamreflector for reflecting the reference beam coming from the firstsplitter; an optical path length adjuster for adjusting an optical pathlength of the reference beam reflected from the reference beamreflector; a reference beam transmitting member for transmitting thereference beam coming from the first splitter to a reference beamirradiation position from which the reference beam is irradiated ontothe reference beam reflector; a first to an nth measuring beamtransmitting member for transmitting the first to the nth measuring beamcoming from the second splitters to measuring beam irradiating positionsfrom which the measurement beams are irradiated onto a first to an nthmeasurement points of a temperature measurement object; a photodetectorfor measuring an interference between the reference beam reflected fromthe reference beam reflector and the first to the nth measuring beamreflected from the temperature measurement object, wherein the opticalpath lengths of the first to the nth measuring beam from the secondsplitter to the temperature measurement object are different from eachother; and an AC component extractor that extracts an AC component froman output signal of the photodetector.

In the above aspects of the present invention, it is preferable that thetemperature measurement object is a substrate to be processed by asubstrate processing apparatus, and the first to the nth measuring beamtransmitting member are arranged in the substrate processing apparatussuch that the first to the nth measuring beam are irradiated onto aplurality of measurement points in a surface of the substrate.

In the first and the third aspect of the present invention, it ispreferable that the temperature measurement object is a substrate to beprocessed by a substrate processing apparatus including a plurality ofprocess chambers in each of which a process is performed on thesubstrate,

wherein the first to the nth measuring beam transmitting member arearranged in each of the process chambers such that the first to the nthmeasuring beam are irradiated onto a plurality of measurement points ina surface of the substrate, and a plurality of the second splitters arerespectively provided for the process chambers, wherein a selector isprovided between the first splitter and the second splitters forselecting one of the second splitters to be used, and wherein thetemperature measuring apparatus is capable of measuring a temperature ofthe substrate in the process.

In the first and the third aspect of the present invention, it ispreferable that the temperature measurement object is a substrate to beprocessed by a substrate processing apparatus including a plurality ofprocess chambers in each of which a process is performed on thesubstrate, wherein the first to the nth measuring beam transmittingmember are arranged in each of the process chambers such that the firstto the nth measuring beam are irradiated onto a plurality of measurementpoints in a surface of the substrate, and a plurality of the secondsplitters are respectively provided for the process chambers, wherein athird splitter is provided between the first splitter and the secondsplitters, which divides the measurement beam coming from the firstsplitter into divided beams to thereby output the divided beams to thesecond splitters, respectively, and wherein the temperature measuringapparatus is capable of measuring a temperature of the substrate in theprocess.

In accordance with a fourth aspect of the present invention, there isprovided a temperature measuring method, including irradiating a firstto an nth measuring beam whose optical path lengths are different fromeach other onto respective measurement points of a temperaturemeasurement object while irradiating a reference beam onto a referencebeam reflector; attenuating the reference beam reflected from thereference beam reflector such that an intensity thereof becomes closer atotal intensity of the first to the nth measuring beam by using anattenuator; measuring interferences between the attenuated referencebeam reflected from the reference beam reflector and the first and thenth measuring beam reflected from the temperature measurement objectwhile moving the reference beam reflector in one direction to therebychange an optical path length of the reference beam reflected from thereference beam reflector; and measuring temperatures at the respectivemeasurement points of the temperature measurement object based on theresults of measuring the interferences.

It is preferable that the attenuator attenuates a light beam passingtherethrough to 1/√{square root over (n)} of an original intensitythereof.

In accordance with the present invention, it is possible to provide atemperature measurement apparatus and method capable of simultaneouslymeasuring temperatures of a plurality of measurement points with ahigher accuracy than in the prior art, and efficiently performing asubstrate process or the like with a higher accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS

The above features of the present invention will become apparent fromthe following description of the embodiments, given in conjunction withthe accompanying drawings, in which:

FIG. 1 is a block diagram illustrating a schematic configuration of atemperature measurement apparatus in accordance with an embodiment ofthe present invention;

FIGS. 2A to 2D are views for explaining the relationship between anintensity of a reference beam and that of a measurement beam;

FIG. 3 is a block diagram illustrating a schematic configuration of atemperature measurement apparatus in accordance with another embodimentof the present invention;

FIG. 4 is a block diagram illustrating a schematic configuration of atemperature measurement apparatus in accordance with still anotherembodiment of the invention;

FIG. 5 is a block diagram illustrating a schematic configuration of atemperature measurement apparatus in accordance with still anotherembodiment of the invention;

FIG. 6 is a block diagram illustrating a schematic configuration of atemperature measurement apparatus in accordance with still anotherembodiment of the invention;

FIGS. 7 to 9 are cross-sectional views for explaining a method ofdetecting an initial peak position;

FIGS. 10A and 10B present a flow chart for explaining a method ofdetecting an initial peak position;

FIG. 11 is a view for explaining a method of detecting an initial peakposition;

FIGS. 12A to 12D are views for explaining a method of detecting aninitial peak position;

FIGS. 13A and 13B present a flow chart for explaining a method ofdetecting an initial thickness;

FIGS. 14A and 14B present a flow chart for explaining a method ofdetecting a temperature;

FIGS. 15A and 15B present a flow chart for explaining a method ofdetecting an initial peak position in a plurality of process chambers;and

FIGS. 16A to 16C present a flow chart for explaining a method ofdetecting an initial thickness in a plurality of process chambers.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail with reference to the accompanying drawings, which form a parthereof. In addition, throughout the following description and theaccompanying drawings, like reference numerals designate likecomponents, and the descriptions thereof will not be repeated.

FIG. 1 shows a block diagram showing a schematic configuration of atemperature measurement apparatus 100 in accordance with an embodimentof the present invention. As shown therein, the temperature measurementapparatus 100 includes a light source 110; a first splitter 120 fordividing a light beam emanated from the light source 110 into areference beam and a measurement beam for temperature measurement; asecond splitter 130 for dividing the measurement beam coming from thefirst splitter 120 into a first to an nth measuring beam; a referencebeam reflector 140 for reflecting the reference beam coming from thefirst splitter 120; and an optical path length adjuster 150 for varyingan optical path length of the reference beam reflected from thereference beam reflector 140.

The optical path length adjuster 150 includes a linear stage 151 formoving the reference beam reflector 140 (which has, for example, areference mirror) in a direction parallel to an incident direction ofthe reference beam; a motor 152; and a He—Ne laser encoder 153. Asdescribed above, by driving the reference mirror in one direction, theoptical path length of the reference beam reflected from the referencemirror can be varied. The motor 152 is controlled by a controller 170via a motor controller 155 and a motor driver 154. In addition, a signalfrom the He—Ne laser encoder 153 is converted into a digital signal byan A/D converter 172, and then is inputted to the controller 170.

Further, the temperature measurement apparatus 100 includes aphotodetector 160 for measuring the interference between: (a) the firstto nth measuring beams reflected from a temperature measurement object10 after the first to nth measuring beams are irradiated onto a first toan nth measurement point of the temperature measurement object 10 suchas a semiconductor wafer, and (b) the reference beam reflected from thereference beam reflector 140 after the reference beam is irradiated ontothe reference beam reflector 140.

The kind of light adopted by the light source 110 is not particularlylimited, so long as the interference between the measuring beams and thereference beam can be measured. When the temperature measurement of thesemiconductor wafer as the temperature measurement object 100 isperformed, the light may preferably be chosen such as not to cause aninterference between two reflected beam beams reflected respectively ata front surface of the semiconductor wafer and a rear surface of thesemiconductor wafer (the distance therebetween is, typically, about 800to 1500 μm).

Specifically, it is preferable to use a low coherence light. The lowcoherence light is a kind of light having a short coherence length. Forexample, a center wavelength of the low coherence light may preferablybe 0.3 to 20 μm; and more preferably, 0.5 to 5 μm. Further, thecoherence length may preferably be 0.1 to 100 μm; and more preferably, 3μm or less. By using the low coherence light for the light source 110,it is possible to avoid problems due to the presence of unwantedinterference, and it becomes easier to measure the interference betweenthe reference beam and the measurement beam reflected from a surface oran inner layer of the semiconductor wafer.

The light source using the low coherence light may be a superluminescent diode (SLD), an light emitting diode (LED), a highbrightness lamp (a tungsten lamp, a xenon lamp and the like), anultra-wideband wavelength light source or the like. Among these lowcoherence light sources, an SLD having a high brightness (whosewavelength is, for example, 1300 nm) may preferably be used as the lightsource 110.

As the first splitter 120, an optical fiber coupler may be used.However, it is not particularly limited so long as it can divide a lightbeam into a reference beam and a measurement beam. In addition, as thesecond splitter 130, an optical fiber coupler may be used as well.However, it is also not particularly limited so long as it is capable ofdividing the measurement beam into a first to an nth measuring beam.Alternatively, an optical waveguide demultiplexer, a semi-transparentmirror and the like may also be employed as the first splitter 120 andthe second splitter 130.

The reference beam reflector 140 includes, for example, a referencemirror. A corner cube prism, a plane mirror and the like may be adoptedas the reference mirror. Among them, a corner cube prism may preferablybe used when the reflected beam needs to be parallel to the incidentlight. However, without being limited thereto, the reference beamreflector 140 may be configured with other devices (for example, opticaldelay lines) so long as they can reflect the reference beam.

As the photodetector 160, a photodiode may be used in consideration of alow price and a good compactness. Specifically, the photodetector 160may be formed of a photodetector (PD) using, for example, a Siphotodiode, an InGaAs photodiode, a Ge photodiode and the like. However,without being limited thereto, the photodetector 160 may be constitutedof other devices such as an avalanche photodiode, a photomultiplier tubeand the like, so long as they can measure the interference between themeasurement beam reflected from the temperature measurement object 10and the reference beam reflected from the reference beam reflector 140.A detection signal of the photodetector 160 is inputted to the A/Dconverter 172 via an amplifier 171 to be converted into a digitalsignal, and then is processed by the controller 170.

The reference beam coming from the first splitter 120 is guided to areference beam irradiation position (from which the reference beam isirradiated onto the reference beam reflector 140) via a reference beamtransmitting member such as a collimator fiber Fz. Thus, the first tonth measuring beams coming from the second splitter 130 are guided to ameasuring beam irradiating positions (from which the measuring beams areirradiated onto the temperature measurement object 10) via a first to annth measuring beam transmitting member such as collimator fibers F1 toFn. However, the first to nth measuring beam transmitting members arenot limited thereto; and may be, for example, optical fibers havingcollimators attached thereto at front ends thereof.

In the temperature measurement apparatus 100, the first to nth measuringbeams have different optical path lengths from the second splitter 130to the temperature measurement object 10. Specifically, if the lengthsof the collimator fibers F1 to Fn are identical to each other, front endsurfaces of the collimator fibers F1 to Fn (whose positions are themeasuring beam irradiating positions) are arranged such that thedistances between the temperature measurement object 10 and the frontend surfaces of the collimator fibers F1 to Fn are different from eachother approximately in the irradiating direction. Further, it is alsopossible to set the optical path lengths of the first to nth measuringbeam to be different from each other by varying the lengths of thecollimator fibers F1 to Fn or the optical fibers without arranging thefront end surfaces of the collimator fibers F1 to Fn to be spatiallydeviated as above.

Further, when the first to nth measuring beam transmitting members arearranged to be deviated from each other approximately in the irradiatingdirection with respect to the temperature measurement object 10, it isnecessary to prevent an overlapping of two or more interference wavesinduced by the individual measuring beams in cooperation with thereference beam, wherein the interference waves are to be measured forrespective measurement points. If, for example, a low coherence lightsource is used as the light source 110, it is possible to prevent suchan overlapping of the interference waves by arranging the first to nthmeasuring beam transmitting members such that the distances between thetemperature measurement object 10 and the respective measuring beamsdiffer from each other by at least the coherence length of theinterference wave.

Furthermore, it is preferable that the positions at which the first tonth measuring beam transmitting members are located are set byconsidering the thickness of the temperature measurement object, therate of change in thickness, the temperature range to be measured, themoving distance (i.e., displacement) of the reference mirror and thelike. Specifically, in case of a silicon wafer having a thickness ofabout 0.7 mm, the moving distance of the reference mirror in atemperature range from a room temperature to 200° C. is about 0.04 mm.Therefore, in this case, the first to nth measuring beam transmittingmembers may be arranged to be spatially deviated from each other in theirradiating direction with intervals of about 0.1 mm. In this manner,the interference waves can be prevented from being superimposed on eachother at the measurement points.

Thus, by irradiating onto the reference beam reflector 140 only once,the interference waves can be detected simultaneously at the measurementpoints onto which the first to nth measuring beams are irradiated.Therefore, the time required for the temperature measurement can bereduced.

In the temperature measurement apparatus 100 in accordance with thepresent embodiment, an attenuator 180 is provided as a light attenuationmeans in an optical path of the reference beam branched off at the firstsplitter 120. The attenuator 180 attenuates the reference beam such thatthe intensity of the reflected beam of the reference beam becomes closerto the total intensity of the reflected beams of the first to nthmeasuring beams. Specifically, as shown in FIG. 1, the attenuator 180may be configured such that the intensity of a light beam having passedtherethrough is attenuated to, e.g., about 1/√{square root over (n)} ofthe original intensity.

In case of providing the attenuator 180, the intensity of the reflectedbeam of the reference beam entering the photodetector 160 is about(1/2)²×(1/n) of the original intensity of the light generated from thelight source 100, since the intensity is attenuated by the factor of(1/2)² by passing through the first splitter 120 two times, and again bythe factor of 1/n by passing through the attenuator 180 two times.Further, the reflectivity of the reference beam reflector 140 is set tobe about 1.

Meanwhile, if the reflectivity of the temperature measurement object 10is R, the reflected beam of the measurement beams entering thephotodetector 160 is attenuated by the factor of (1/2)² by passingthrough the first splitter 120 two times, and again by the factor of(1/n)² (for example, 1/16 when n=4) by passing through the secondsplitter 130 two times. Therefore, the resultant factor of theattenuation is about (1/2)²×(1/n)²×R×n=(1/2)²×(1/n)×R, because there aren number of the reflected beams of the measuring beams, each of whichundergoes the reflectivity of R.

Therefore, the difference between the intensity of the reflected beam ofthe reference beam and that of the reflected beams of the first to nthmeasuring beams occurs only by the reflectivity R of the temperaturemeasurement object 10. As a result, it is substantially same as the caseof a one-point measurement in which the second splitter 130 is notprovided.

As shown in FIG. 2A, in case of the one-point measurement, the intensityof the reflected beam of the measurement beam is R if the intensity ofthe reflected beam of the reference beam is 1, and the ratio of theintensity of the reference beam to that of the measurement beam includedin a measured waveform is 1:R (i.e., reference beam:measurementbeam=1:R).

Further, as shown in FIG. 2B, in case of the conventional n-pointmeasurement, the intensity of the reflected beam of the measurement beamis R×(1/n) of the intensity of the reflected beam of the reference beam,and the ratio of the intensity of the reference beam to that of themeasurement beam included in a measured waveform is 1:R×(1/n) (i.e.,reference beam: measurement beam=1:R×(1/n)). Therefore, the leveldifference between the reference beam and the measurement beam increasesas the number n becomes larger. Further, the intensity of interferenceis determined by the intensity of the measurement beam. Therefore, whenthe level difference between the reference beam and the measurement beambecomes very large, the intensity of interference becomes negligiblecompared to the intensity of the reference beam, thereby deterioratingthe S/N ratio.

However, in accordance with the temperature measurement apparatus 100 ofthe present embodiment, the intensity of the reflected beam isattenuated by the factor of 1/n by the attenuator 180. Therefore, asshown in FIG. 2C, the ratio of the intensity of the reference beam tothat of the measurement beam included in a measured waveform is 1:R(i.e., reference beam: measurement beam=1:R), which is same as in caseof the one-point measurement. In this manner, the S/N ratio can beenhanced compared to the case of FIG. 2B. Further, although it has beendescribed in the above that the light level is attenuated to 1/√{squareroot over (n)} by the attenuator 180, the attenuation level is notlimited thereto, and may be properly selected otherwise.

Hereinafter, a second embodiment of the present invention will bedescribed with reference to FIG. 3. A temperature measurement apparatus200 shown in FIG. 3 employs a single splitter 220 for splitting a lightbeam emanated from the light source 110, instead of the first splitter120 and the second splitter 130 in FIG. 1. The splitter 220 splits thelight beam generated from the light source 110 into (N+1) number ofbeams including a first to an nth measuring beam and a reference beam.The other parts are the same as those of the temperature measurementapparatus 100 shown in FIG. 1.

As shown in FIG. 2D, in case of employing the temperature measurementapparatus 200, the ratio of the intensity of the reference beam to thatof the measurement beam included in a measured waveform is 1:R×n (i.e.,reference beam: measurement beam=1:R×n, which is approximately the sameas in case of the one-point measurement. In this manner, it is possibleto improve the S/N ratio in comparison with the case of FIG. 2B.

Next, a third embodiment of the present invention will be described withreference to FIG. 4. As shown therein, a temperature measurementapparatus 300 does not include the attenuator 180 in the temperaturemeasurement apparatus 100 of FIG. 1, but instead includes an ACcomponent extractor 310 capable of extracting an AC component from adetection signal of the photodetector 160. In addition, the temperaturemeasurement apparatus 300 further includes a switch 311 for switchingthe state of the AC component extractor 310 between a first state wherethe AC component is extracted by the AC component extractor 310 and asecond state where the total signal passes through the AC componentextractor 310, thereby making it possible to check the DC level (lightintensity). The other parts of the temperature measurement apparatus 300are the same as those of the temperature measurement apparatus 100 shownin FIG. 1.

In accordance with the temperature measurement apparatus 300, the ACcomponent can be extracted by the AC component extractor 310. Thus, theinterference intensity can be measured in AC level without depending onDC level. Therefore, the S/N ratio can be enhanced compared to the caseof FIG. 2B.

Hereinafter, a temperature measurement apparatus 400 and a temperaturemeasurement apparatus 500, which are capable of measuring respectivetemperatures in a plurality of process chambers in a substrateprocessing apparatus, will be described with reference to FIGS. 5 and 6.

In accordance with the temperature measurement apparatus 400 shown inFIG. 5, one among a plurality of (in this example, six) process chambersPC1, PC2, . . . , PC6 is selected by a selector 410 such as an opticaladd/drop multiplexer (OADM) in a manner that it is possible to measure atemperature of each of substrates disposed in the respective processchambers, and, if necessary, a temperature of each of focus rings F/R aswell.

More specifically, a second splitter 130 and a first to an nth measuringbeam transmitting member, e.g., collimator fibers F1 to Fn (n=4 in theexamples of FIGS. 5 and 6) are disposed in each of the process chambersPC1, PC2, . . . , PC6, and the selector 410 is provided between thefirst splitter 120 and each of the six second splitters 130. Byselecting one of the process chambers PC1, PC2, . . . , PC6 forperforming temperature measurement by using the selector 410, thetemperature of each of the process chambers PC1, PC2, . . . , PC6 can bemeasured. In each of the process chambers PC1, PC2, . . . , PC6, aprocess such as etching or film forming is performed on a substrate suchas a semiconductor wafer.

Further, in the temperature measurement apparatus 500 shown in FIG. 6, athird splitter 510 is interposed between a first splitter 120 and secondsplitters 130 provided for a plurality of (e.g., six) process chambersPC1, PC2, . . . , PC6. Thus, a measurement beam, having been branchedoff at the first splitter 120 from a light beam generated by the lightsource 110, is splitted into six divided beams to be sent to each of thesecond splitters 130 for the six process chambers PC1, PC2, . . . , PC6.In this manner, it is possible to measure the temperatures of asubstrate and a focus ring disposed in each of the process chambers PC1,PC2, . . . , PC6.

In the temperature measurement apparatuses 400 and 500, the processchambers PC1, PC2, . . . , PC6 share the light source 110, the firstsplitter 120, a reference beam reflector 140, an optical path lengthadjuster 150, a photodetector 160, a controller 170 and the like inmeasuring the temperature. Therefore, it is possible to suppress anincrease in cost compared to the case where each of the process chambershas its own temperature measurement apparatus. In addition, since asingle controller 170 can manage the whole measurement data, it ispossible to save the time and cost required for the data management.

In accordance with the temperature measurement apparatus 400 or 500, thecontroller 170 stores in advance interference position data for theprocess chambers PC1, PC2, . . . , PC6, respectively; and, whennecessary, retrieves the interference position data to thereby use thedata for the process chambers PC1, PC2, . . . , PC6. Further, in case ofmeasuring temperatures at a plurality of measurement points in theprocess chambers PC1, PC2, . . . , PC6, the controller 170 stores inadvance each of interference position data for the measurementpositions; and, when necessary, retrieves the interference position datato thereby use the data for the process chambers PC1, PC2, . . . , PC6.

Hereinafter, a method of measuring interference positions (initial peakpositions) of the measurement points will be described. As shown in FIG.7, a wafer piece 602 is mounted on a mounting table 601 in such a mannerthat a reflected beam is detected only from a specified measurementpoint (e.g., channel CH1 in FIG. 7) to be measured. Alternatively, asshown in FIG. 8, a perforated wafer 603 is mounted on the mounting table601, wherein the perforated wafer 603 has holes in such a manner that areflected beam is detected only from a specified measurement point(e.g., channel CH1 in FIG. 8) to be measured and not from the othermeasurement points. Alternatively, as shown in FIG. 9, arear-surface-treated wafer 604 is mounted on the mounting table 601,wherein the rear surface of the rear-surface-treated wafer 604 istreated such that a strong reflected beam is detected only from aspecified measurement point (e.g., channel CH1 in FIG. 9) to bemeasured, and light reflection is weak from the other measurementpoints. In any of the above cases, a reflected beam is substantiallydetected from only a specified measurement point (channel CH1) to bemeasured.

Thereafter, an initial peak position is detected under the control ofthe controller 170 as follows. At first, as shown in a flow chart ofFIGS. 10A and 10B, measurement conditions including the number ofchannels, a stage velocity, a measurement pitch, an initial temperature,a port number, a peak detection range, a peak proximity range, thenumber of peaks to be used, a channel to be measured and an expectedfinal temperature are inputted (step 701); and then the measurement isstarted (YES in step 702).

Next, the controller 170 starts moving the linear stage 151 to acounter-motor side limit (i.e., a location that minimizes an opticalpath length of the reference beam), and monitors the stage position andthe driving state (step 703). Then, the controller 170 stops the drivingwhen the relocation of the stage is completed (YES in step 704).

Thereafter, the controller 170 starts moving the linear stage 151 towarda motor side limit which is a limit located opposite to thecounter-motor side limit (step 705); and initiates the sampling of theA/D converter 172 (step 706). At this time, the controller 170calculates a sampling number such that the sampling is stoppedimmediately before the limit.

When the sampling is completed (YES in step 707), the controller 170starts a deceleration and stoppage of the linear stage 151 (step 708);and stops the driving of the linear stage 151 (YES in step 709).

Subsequently, the controller 170 starts moving the linear stage 151 tothe counter-motor side limit (step 710).

Further, the controller 170 executes a waveform analysis to calculate aninitial peak position, an initial stage position and awaveform-estimated distance. Herein, the waveform-estimated distance iscalculated as follows: (waveform-estimated distance)=(maximumpeak-detected distance)−(minimum peak-detected distance)+(stagedisplacement at acceleration and deceleration). The controller storesthe results for each channel, and shows the waveform (step 711).

Next, the controller 170 determines whether there is any overlapping inpeak position (step 712). Then, the controller 170 displays “normal” ifthere is no overlapping in peak position (step 713); and display “alarm”if there is a peak position overlapping (step 714).

Subsequently, the controller 170 determines whether a measurement ofother channel is to be performed (step 715). Then, if the measurement isto be performed on other channel, the above steps are repeated. However,if there is no other channel to be measured, the controller 170 finishesthe process (step 716).

FIG. 11 shows an example of a measured waveform obtained for onemeasurement point (channel) as described above. Herein, the Y-axisrepresents an output level of a photodetector, and the X-axis representsa displacement of a mirror functioning as a reference beam reflector.

In the above-discussed method for an initial peak position detection,the sampling of data is performed from the time when the linear stage151 is located at one limit position (a location that minimizes theoptical path length of the reference beam) such as a counter-motor sidelimit in FIG. 1 until the displacement of the linear stage 151 coversthe total driving range. Therefore, it is possible to execute a peakposition detection even when the thickness of the temperaturemeasurement object 10 is unknown.

Regarding a first peak, the controller 170 detects a maximum outputlevel among the entire data, and determines that the first peak islocated at the peak center of a first peak range extending between themaximum output position±a certain width (μm). Regarding a second peak,the controller 170 detects a maximum output level among all the datathat follows the end point of the first peak range, and determines thatthe second peak is located at a peak center of a second peak rangeextending between the second maximum output position±a certain width(μm). Further, regarding a third peak, the controller 170 detects amaximum value among all the data that follows the end point of thesecond peak range, and determines that the third peak is located at apeak center of a third peak range extending between the third maximumvalue±a certain width (μm). The detection of the peak center isperformed by acquiring a center position of a squared waveform whoseamplitude is equal to the square of that of the original waveform.

FIGS. 12A to 12D show exemplary waveform data obtained for themeasurement points CH1 to CH3 as described above. Herein, the Y-axisrepresents an output level of the photodetector, and the X-axisrepresents a displacement of a mirror functioning as the reference beamreflector. As shown therein, the controller 170 adjusts an optical pathlength to prevent the peak positions from overlapping each other,thereby making it possible to identify a peak from each measurementpoint (especially refer to FIG. 12D).

After detecting the initial peak position in this manner, an initialthickness measurement of the temperature measurement object is performedbefore measuring the temperature. The temperature of the temperaturemeasurement object is detected by a change in thickness of thetemperature measurement object with respect to the initial thickness.

The initial thickness measurement will be described with reference toFIGS. 13A and 13B. First, the number of channels, a stage velocity, ameasurement pitch, a port number and an initial temperature areinputted. Then, it is selected how many number of measurements are to beaveraged (step 801).

Next, the user determines whether the initial thickness and temperatureare to be inputted manually (step 802). If the user already knows theinitial thickness and temperature, and is to input them manually, step816 is performed, which will be described later. However, if the initialthickness and temperature are not to be inputted manually, themeasurement is started (YES in step 803); and the initial position dataand the measurement distance data are retrieved for each of themeasurement points (channels) (step 804).

Thereafter, the linear stage 151 is started to be moved to a minimuminterchannel start position (step 805). When the linear stage 151arrives at the minimum interchannel start position, it is started tomove the linear stage 151 toward a motor side limit (step 806).

Further, the A/D converter 172 is started (step 807) to thereby performthe sampling (step 808). At this time, the number of samplings iscalculated such that the sampling is stopped at a maximumwaveform-estimated interchannel distance+α.

When the sampling is completed (YES in step 809), the velocity of thelinear stage 151 is reduced (step 810) to thereby stop the driving ofthe linear stage 151 (YES in step 811).

Subsequently, it is started that the linear stage 151 is moved to anminimum interchannel start position (step 812).

Further, the initial peak position is retrieved for each measurementchannel to perform the waveform analysis, and displays the peakposition, the inter-peak distance, temperature estimation and waveform(step 813).

Next, it is determined whether the linear stage 151 has reached theminimum interchannel start position (step 814), and then whether themeasurement has been repeated for a given number of times (step 815).After repeatedly performing the measurement for the given number oftimes, an average of inter-peak distance is obtained (step 816), andthen the procedure enters a state of waiting for a temperaturemeasurement (step 817).

Otherwise, if the initial thickness and temperature are already known,they are manually inputted (step 802). Then, an average of inter-peakdistance is obtained (step 816), and then the procedure enters the stateof waiting for a temperature measurement (step 817).

As a result, it is possible to detect the initial peak position andmeasure the temperature after the initial thickness measurement. Thetemperature measurement will now be described with reference to FIGS.14A and 14B.

In this example, the temperature measurement is prepared in a statewhere the settings of the initial thickness measurement are maintained(step 901). Then, a location to store data, the number of measurementsand a peak proximity range are inputted (step 902).

When the input is completed, the measurement is started (YES in step903), and the linear stage 151 is started to be moved to the minimuminterchannel start position (step 904). When the linear stage 151arrives at the minimum interchannel start position, the linear stage 151is started to be moved toward the motor side limit (step 905).

Subsequently, the A/D converter is started (step 906) to thereby performthe sampling (step 907). At this time, the number of sampling iscalculated such that the sampling is stopped at a maximumwaveform-estimated interchannel distance+α.

When the sampling is completed (YES in step 908), the velocity of thelinear stage 151 is reduced (step 909) to thereby stop the driving ofthe linear stage 151 (step 910).

Thereafter, the linear stage 151 is started to be moved to an minimuminterchannel start position (step 911).

Thereafter, the waveform analysis is performed, the inter-peak distanceis calculated from the peak positions, the temperature is estimated fromthe inter-peak distance, the waveform is shown, and the measurement datais stored (step 912).

Next, it is determined whether the linear stage 151 arrives at theminimum interchannel start position (step 913), and then whether themeasurement has been repeated for a given number of times (step 914).After repeatedly performing the measurement for the given number oftimes, the measurement is finished (step 915).

Hereinafter, the temperature measurement apparatuses 400 and 500 shownin FIGS. 5 and 6 that can measure the temperature in the plurality ofprocess chambers will be described. FIGS. 15A and 15B describe a methodof detecting an initial peak position under the control of thecontroller 170.

First, a process chamber (PC) number is selected (step 750). Then, thefollowing steps 751 to 765 are performed. Steps 751 to 765 aresubstantially the same as steps 701 to 715 in FIGS. 10A and 10B, exceptthat, in step 761, data including an initial peak position and the likeare stored for each of the measurement channels corresponding to theselected PC number.

Thereafter, at the end of the procedure, it is determined whether otherprocess chamber is to be measured (step 766); and, if there is no otherprocess chamber to be measured, the measurement is finished (step 767).

FIGS. 16A to 16C explain a method of measuring an initial thicknessunder the control of the controller 170 in accordance with thetemperature measurement apparatuses 400 and 500 capable of measuringtemperatures in the plurality of process chambers.

First, the PC number is selected (step 850). Then, the following steps851 to 866 are performed. Steps 851 to 866 are substantially the same assteps 801 to 816 in FIGS. 13A and 13B except the following: in step 854,initial position data of each measurement channel corresponding to theselected PC number are retrieved; and, in step 863, initial positiondata of each measurement channel corresponding to the selected PC numberare retrieved. At the end of the procedure, it is determined whetherother process chamber is to be measured (step 867); and, if there is noother process chamber to be measured, the procedure enters a state ofwaiting for the temperature measurement (step 868).

In the temperature measurement apparatuses 400 and 500 for measuringtemperatures in a plurality of process chambers, the temperaturemeasurement processes after the state of waiting for the temperaturemeasurement (step 868) in FIG. 16C is substantially the same as thoseshown in FIGS. 14A and 14B of the above.

In the temperature measurement apparatuses 100 and so on, the light beamgenerated from the light source 110 enters the first splitter 120, whichdivides it into a measurement beam and a reference beam. Among these,the measurement beam is divided into first to nth measuring beams by thesecond splitter 130 to be irradiated onto the temperature measurementobject 10 such as a semiconductor wafer at each measurement point,thereby being reflected by a front surface, an interface surface or arear surface of each layer.

Meanwhile, the reference beam is reflected by the reference beamreflector 140. Then, the reflected beams of the first to nth measuringbeams enter the first splitter 120 by way of the second splitters 130,thereby being detected by the photodetector 160 together with thereflected beam of the reference beam.

Further, by scanning the reference beam reflector 140, it is possible toobtain interference waveforms shown in FIGS. 12A to 12D, in which theY-axis represents the output level of the photodetector 160 and theX-axis represents the displacement of the reference beam reflector 140.Herein, the low coherence light source as described above is used as thelight source 110. Since the coherence length of the light emanatedtherefrom is short, a strong interference occurs at such locations wherethe optical path length of the measurement beam is equivalent to that ofthe reference beam, and interference hardly occurs at the otherlocations.

For this reason, by moving the reference beam reflector 140 to vary theoptical path length of the reference beam, the reflected reference beaminterferes with the reflected measurement beam reflected from a frontand a rear surface of the temperature measurement object 10, and, ifinner layers exist therein, from each of the inner layers due to adifference in refractive index.

In the examples shown in FIGS. 12A to 12D, as the reference beamreflector 140 is scanned, the following sequence is observed. First, aninterference wave is generated by the interference between a reflectedreference beam and a reflected beam from one surface (a front or rearsurface) at the measurement point P1 in the temperature measurementobject 10. Then, another interference wave is generated by theinterference between a reflected reference beam and a reflected beamfrom one surface (a front or rear surface) at the measurement point P2in the temperature measurement object 10. Thereafter, anotherinterference wave is generated by the interference between a reflectedreference beam and a reflected beam from one surface (a front or rearsurface) at the measurement point P3 in the temperature measurementobject 10.

As the scanning of the reference beam reflector 140 is furthercontinued, an interference wave is generated by the interference betweenthe reflected reference beam and the reflected beam from an interfacesurface of an inner layer at each of the measurement points P1, P2 andP3. Finally, an interference wave is generated by the interferencebetween the reflected reference beam and the reflected beam from theother surface (a rear or front surface) at each of the measurementpoints P1, P2 and P3. In this manner, simply by scanning the referencebeam reflector 140 one time, interference waves from differentmeasurement points can be measured at the same time.

Hereinafter, an explanation will be given on a method of measuring thetemperature based on the interference wave induced by the interferencebetween the measurement beam and the reference beam. Methods ofmeasuring the temperature based on the interference wave include, forexample, a temperature conversion method using a change in the opticalpath length caused by a temperature change. In the following, atemperature conversion method using a position shift of the interferencewaveform will be explained.

When the temperature measurement object 10 such as a semiconductor waferis heated by a heater or the like, the temperature measurement object 10expands, so that its refractive index is changed. Therefore, theposition of the interference waveform is shifted, and the intervalbetween peaks in the interference waveform is changed after thetemperature change. In this case, if there occurs a temperature changein each of the measurement points, the position of the interferencewaveform is shifted at each measurement point, thereby changing theinterval between peaks in the interference waveform.

Therefore, by measuring the interval between the peaks in theinterference waveform for each measurement point, a temperature changehaving occurred at each of the measurement points can be detected. Incase of, for example, the temperature measuring apparatus 100 shown inFIG. 1, the interval between the peaks in the interference waveformdepends on the moving distance of the reference beam reflector 140(e.g., a reference mirror). Therefore, by measuring the displacementmade by the reference mirror, which corresponds to the interval betweenthe peaks of the interference waveform, a temperature change can bedetected.

If the thickness of the temperature measurement object 10 is d, and itsrefractive index is n, a shift of peak position in the interferencewaveform depends on a linear expansion coefficient α of each layer inrelation to the thickness d, and also depends on a temperaturecoefficient β of refractive index change of each layer in relation to achange in the refractive index n. Further, it is known that thetemperature coefficient β of refractive index change depends on thewavelength.

Therefore, the thickness d′ of the wafer after a temperature change at acertain measurement point P is represented as the following equation Eq.(1). Herein, ΔT represents a temperature change at a measurement point,α represents a linear expansion rate, and β represents a temperaturecoefficient of refractive index change. Further, d and n represent athickness and a refractive index at the measurement point P before thetemperature change, respectively.

d′=d(1+αΔT),n′=n(1+βΔT)  Eq. (1)

As can be seen from Eq. (1), the optical path length of the measurementbeam passing through the measurement point P is changed by a change intemperature. In general, the optical path length is defined by a productof the thickness d and the refractive index n. Therefore, if the opticalpath length of the measurement beam passing through the measurementpoint P before the temperature change is L, and the optical path lengthafter the temperature is changed by ΔT at the measurement point is L′, Land L′ are represented as the following equation Eq. (2).

L=d·n,L′=d′·n′  Eq. (2)

Accordingly, a difference L-L′ between the optical path length of themeasurement beam before the temperature change and that aftertemperature change at the measurement point can be calculation by Eqs.(1) and (2). Thus calculated result is summarized by the followingequation Eq. (3), where minor terms are omitted in consideration ofα·β<<α and α·β<<β.

$\begin{matrix}\begin{matrix}{{L^{\prime} - L} = {{d^{\prime} \cdot n^{\prime}} - {d \cdot n}}} \\{= {{d \cdot n \cdot \left( {\alpha + \beta} \right) \cdot \Delta}\; T}} \\{= {{L \cdot \left( {\alpha + \beta} \right) \cdot \Delta}\; T\; 1}}\end{matrix} & {{Eq}.\mspace{14mu} (3)}\end{matrix}$

In the above, the optical path length of the measurement beam for eachmeasurement point corresponds to a width between peaks of theinterference waveform induced by the measuring beam and the referencebeam. Therefore, if a linear expansion rate α and a temperaturecoefficient β of refractive index change are known in advance, theoptical path length can be converted into the temperature of eachmeasurement point using Eq. (3) by measuring the width between the peaksof the interference waveform at each measurement point.

As described above, if the temperature is converted from theinterference wave, the optical path length determined by the inter-peakwidth of the interference waveform varies according to the linearexpansion rate α and the temperature coefficient β of refractive indexchange, the linear expansion rate α and the temperature coefficient β ofrefractive index change needs to be acquired in advance.

In a certain temperature range, the linear expansion rate α and thetemperature coefficient β of refractive index change of a specifiedmaterial (e.g., a semiconductor wafer) may vary with the temperature aswell. For example, within a temperature range from about 0 to 100° C.,the linear expansion rate a does not normally change significantly.Therefore, the linear expansion rate can be regarded as a constant inthis range. However, if the temperature exceeds 100° C., the linearexpansion rates of some materials start to change by greater extents asthe temperature becomes higher. Therefore, in some cases, thetemperature dependency of the linear expansion rate cannot be neglected.Similarly, there are also cases where the temperature dependency of thetemperature coefficient β of refractive index change cannot beneglected.

In the case of, for example, silicon (Si) that forms a semiconductorwafer, it is known that the linear expansion rate α and the temperaturecoefficient β of refractive index change can be approximated withquadratic curves within a temperature range from 0 to 500° C. Since thelinear expansion rate α and the temperature coefficient β of refractiveindex change have a temperature dependency of the above, the accuracy inthe temperature conversion can be enhanced by, for example, acquiring inadvance the linear expansion rate α and the temperature coefficient β ofrefractive index change as functions of temperature and taking thusacquired data into consideration.

Further, the temperature measurement method using the interference waveinduced by the measurement beam and the reference beam is not limited tothe method of the above. It is also possible to, for example, use achange in absorption intensity due to temperature change. Further, it isalso possible to combine the method using a change in the optical pathlength change due to temperature change and the method of using a changein absorption intensity due to temperature change.

While the invention has been shown and described with respect to theembodiments, it will be understood by those skilled in the art thatvarious changes and modifications may be made without departing from thescope of the invention as defined in the following claims.

What is claimed is:
 1. A temperature measuring apparatus comprising: alight source; a single splitter for dividing a light beam emanated fromthe light source into a reference beam and a first to an nth measuringbeam, n being larger than 1; a reference beam reflector for reflectingthe reference beam coming from the splitter; an optical path lengthadjuster for adjusting an optical path length of the reference beamreflected from the reference beam reflector; a reference beamtransmitting member for transmitting the reference beam coming from thesplitter to a reference beam irradiation position from which thereference beam is irradiated onto the reference beam reflector; a firstto an nth measuring beam transmitting member for transmitting the firstto the nth measuring beam coming from the splitter to measuring beamirradiating positions from which the measurement beams are irradiatedonto a first to an nth measurement points of a temperature measurementobject; and a photodetector for measuring an interference between thereference beam reflected from the reference beam reflector and the firstto the nth measuring beam reflected from the temperature measurementobject, wherein the optical path lengths of the first to the nthmeasuring beam from the splitter to the temperature measurement objectare different from each other.
 2. The temperature measuring apparatus ofclaim 1, wherein the apparatus is configured to measure temperature of asubstrate to be processed by a substrate processing apparatus as thetemperature measurement object, and the first to the nth measuring beamtransmitting member are arranged in the substrate processing apparatussuch that the first to the nth measuring beam are irradiated onto aplurality of measurement points in a surface of the substrate.